Development and characterization of monoclonal antibodies against FMD virus type Asia-1 and determination of antigenic variations in the field strains

Twelve mouse monoclonal antibodies (MAbs) were developed against an Indian vaccine strain of foot and mouth disease virus (FMDV) type Asia-1 WBN 117/85. The MAbs were tested for their ability to bind to whole virus particle, trypsin-treated 146S (TT-146S) virus particle, sub-viral (12S and disrupted virus) antigens by ELISA and to neutralize virus infectivity in cell culture. Extensive characterization of MAbs revealed the existence of three different groups based on the binding of non-overlapping epitopes. Eight type Asia-1 specific MAbs (RF7, RF8, RD10, RE11, RC11, RC10/O, RB11 and RC10/M), which formed group 1 (G1), were found to bind a neutralizing, trypsin-sensitive (TS) and conformational epitope. Two MAbs (WB8 and WC3) in group 2 (G2) were found to bind a non-neutralizing, trypsin-resistant, conformational and 12S-specific epitope, which was intertypically conserved in all the four serotypes of FMDV (O, A, C and Asia-1) prevalent in India. Two MAbs (KG10 and KF10), which formed group 3 (G3), were found to be against a non-neutralizing, TS and conformational epitope, common to types Asia-1 and A. Members of G1 were IgG2a isotype, while those of G2 and G3 were IgG1 and IgG2b isotypes, respectively. Antigenic analysis of 31 FMDV type Asia-1 field isolates and two vaccine strains, using a panel of type Asia-1-specific MAbs, revealed antigenic similarity of the virus isolates tested and non-existence of neutralization escape mutants. The developed MAbs have practical utility, especially in the manufacture of FMD vaccine, diagnosis and FMDV characterization.